1. Field of the Invention
This invention relates to a driving method and driving device for driving a polyphase inverter.
2. Description of the Related Art
FIG. 1 illustrates a conventional three-phase inverter 900 that includes three inverter legs, each of which has upper and lower transistors (M1 and M2, M3 and M4, and M5 and M6). The transistors (M1 to M6) of the conventional three-phase inverter 900 are switched on and off by driving signals (S1 to S6) generated by a driving device 950 to thereby permit the conventional three-phase inverter 900 to generate inverter output voltages (Va, Vb, Vc), whereby three sinusoidal signals that have equal amplitudes and that are 120° out of phase are generated. The driving device 950 typically uses a sinusoidal pulse width modulation (SPWM) technique or a space vector PWM (SVPWM) technique to generate the driving signals (S1 to S6). However, the number of times the transistors (M1 to M6) of the conventional three-phase inverter 900 are switched on and off when driven by the driving signals (S1 to S6) generated by the driving device 950 is determined by the carrier frequency of the driving device 950, is fixed, and is relatively high. This increases power consumption, and thus decreases efficiency of the conventional three-phase inverter 900.